The present invention is generally related to permanent magnet linear brakes and is more particularly directed to eddy brake systems for movable cars, for example, rail supported cars, go-carts, elevator cars, conveyor cars, and roller coaster cars, among others.
As a specific example, the majority of hereinbefore constructed entertainment rides, such as roller coasters, have relied on friction brakes for deceleration and stopping of wheel-mounted cars. However, due to friction, such brakes are subject to wear and must be regularly monitored and serviced to maintain proper operating conditions.
Linear eddy current brakes would be a preferable replacement for such friction brakes inasmuch as no contact is made with the rail for braking and consequently, they are free from wear due to friction. Eddy current brakes are based on the law of induction. When a conductive member is moved through a magnetic field, eddy currents are generated in the member and a secondary magnetic field caused by the eddy currents is opposed to the magnetic field through which the member passes. The resulting force component acts opposite to the traveling direction of the member.
Electromagnetic coils may be utilized to generate the magnetic field for inducing eddy currents in the moving member, however, such electromagnetic systems require elaborate controllers in order to excite the coils at a proper time to effect the braking. Accordingly, it is more preferable to effect eddy current braking through the use of permanent magnets.
Hereinbefore, permanent magnetic linear eddy current brake systems have utilized two arrays of magnets attached to stationary rails with a conducting fin disposed on a moving object and arranged to pass through a gap provided between the two arrays of magnets. As the fin is passed through the magnet arrays, an electric eddy current is induced therein which reverses as the fin passes from a magnet of one polarity to a magnet of opposite polarity. As hereinabove noted, a force is then created and exerted on the fin which causes a braking force. Other prior art devices include Free Fall Towers which utilize two arrays of magnets on a car which travels along a stationary fin.
The hereinbefore linear braking systems have utilized two arrays of permanent magnets spaced apart from one another to establish a channel or gap there between the passage of a fin. This structural limitation limits such braking systems to applications on linear, or straight rail sections. Accordingly, there is a need for an eddy current braking systems which can be utilized on curvilinear rail sections and further, it is desirable to utilize a single array of permanent magnets in an eddy current braking system in order to reduce the cost thereof.
Eddy current braking apparatus, in accordance with the present invention, generally includes a single array of permanent magnets which provides a magnetic flux and a electrically conductive means for exclusively engaging the magnetic flux provided by the single array of permanent magnets.
Means are provided, mounting the magnets and the conductive means, for enabling relative motion, between the magnets and the conductive means, to produce eddy currents in the conductive means which result in a braking force between the magnets and the conductive means.
More particularly, the present invention may include a car with the magnets disposed on the car and the conductive means being stationary. In this instance, the conductive means is not limited to a linear configuration but may, in fact, be disposed in a curvilinear relationship. The car in this instance is guided along the appropriate curvilinear path.
Alternatively, the present invention may provide for the conductive means to be disposed in the car and the array of permanent magnets in a stationary position. In this instance, the array of permanent magnets may be disposed in a curvilinear arrangement with an appropriate guiding of the car along the curvilinear path.
Ferromagnetic backing means may be provided which support the conductive means and also provide a holding force between the magnetic means and the conductive means. When employed on the guided car, the ferromagnetic backing means enables a positive holding without relative motion between the magnets and the conductive means.
In another embodiment of the present invention, eddy current braking apparatus for a guided car is provided which includes first magnet means for providing a magnet flux with the first magnet means consisting of a first single array of permanent magnets. A first, electrically-conductive means is provided for exclusively engaging in magnetic flux provided by the first array of permanent magnets.
First means, mounting the first magnetic means and the first conductive means is provided for enabling relative motion between the first magnetic means and the first conductive means in order to produce eddy currents in the first conductive means resulting in a braking force between the first magnet means and the second conductive means.
Further second magnetic means are provided for producing a magnetic flux with the second magnet means consisting of a second single array of permanent magnets. A corresponding second, electrically conductive means is provided for exclusively engaging the second magnetic flux provided by the second single array permanent magnets.
Second means, mounting second magnet means and the second conductive means, is provided for enabling relative motion between the second magnet means and the second conductive means in order to produce eddy currents in the second conductive means resulting in a breaking force between the second magnet means and the second conductive means.
In one embodiment, the first and second magnet means may be disposed on opposite sides of the car and in another embodiment, the first and second conducted means are mounted on opposite sides of the guided car.
In yet another embodiment of the present invention, the permanent magnet array which has an orientation which significantly increases the flux density through one side, or pole face, of the permanent magnet array.